Re: [PATCH] sched: Give idle_balance() a break when it does not move tasks.

[Srikar Dronamraju <srikar@linux.vnet.ibm.com>]

>  	/*
> @@ -5298,6 +5300,8 @@ void idle_balance(int this_cpu, struct rq *this_rq)
>  			continue;
> 
>  		if (sd->flags & SD_BALANCE_NEWIDLE) {
> +			load_balance_attempted = true;
> +
>  			/* If we've pulled tasks over stop searching: */
>  			pulled_task = load_balance(this_cpu, this_rq,
>  						   sd, CPU_NEWLY_IDLE, &balance);
> @@ -5322,6 +5326,10 @@ void idle_balance(int this_cpu, struct rq *this_rq)
>  		 */
>  		this_rq->next_balance = next_balance;
>  	}
> +
> +	/* Give idle balance on this CPU a break when it isn't moving tasks */
> +	if (load_balance_attempted && !pulled_task)
> +		this_rq->next_newidle_balance = jiffies + (HZ / 100);
>  }

Looks reasonable. However should we do this per sd and not per rq. i.e
move the next_newidle_balance to sched_domain. So if we find a
load_balance in newly_idle context that wasn't successful, we skip
load_balance for that sd in the next newly idle balance.

-- 
Thanks and Regards
Srikar Dronamraju